Use of liquefied gas as a fuel source for various applications has gained popularity in recent years due to the lower cost and cleaner burning of gaseous fuels such as liquefied petroleum gas (LPG), compressed natural gas (CNG), or liquefied natural gas (LNG), as compared to more traditional fuels such as gasoline or diesel. In practical applications, for example, mining trucks, locomotives, highway trucks and the like, to gain sufficient range between refueling, the gaseous fuel is stored and carried on-board the vehicle in a liquefied, pressurized, cryogenic state. Before the cryogenically stored fuel is to be used by the engine, it is heated to elevate its temperature from about −160 deg. C. to about 90 deg. C. Moreover, the gaseous fuel is pressurized for injection into the intake system or the engine cylinders to provide sufficient power density.
Well insulated pressure tanks are typically used to store and carry cryogenic fuel in a liquid state on board the vehicle. From there, fuel may be drawn in a liquid state, pressurized, and heated before being provided for use by an engine. However, regardless of the degree of insulation provided by the tank, the fuel stored therein is still subject to heating from the environment. For this reason, typical storage tanks include pressure-regulated vents, which can release fuel in a gaseous state from within the tank such that tank pressure can be controlled. In mobile applications, the vented gas may be released for dispersion in the atmosphere, while in stationary applications the vented gas may be disposed through a flame stack.
The amount of gas that may be disposed in this fashion may depend on numerous factors, for example, the filled state of the tank, ambient temperature, insulation quality of the storage tank, and other factors. It would be desirable to reduce the amount of fuel vented from the tank and thus the cost associated with replacing this fuel for use by the engine.